1. Field of the Invention
The invention relates in general to battery arrays, and, in particular, to self healing dynamically configurable battery arrays that are capable of forming a plurality instantaneous power buses, each of which is configured to the electrical power requirements of specific components or modules (loads) of an electrical circuit, sometimes referred to herein as a xe2x80x9cdigital batteryxe2x80x9d or a xe2x80x9cdynamic battery arrayxe2x80x9d.
2. Description of the Prior Art
Electronic devices are becoming more and more complex. Such complex electronic devices typically contain a plurality of different components or modules (loads), each of which has its own unique voltage and current requirements. As used herein xe2x80x9cloadxe2x80x9d includes components, modules, separately powered elements of components, and the like. Batteries typically supply power having a predetermined nominal value to a common bus. Power for the individual components is drawn from the common bus and passed through various power conditioning components to provide each of the operative components with the particular current and voltage values that the specific component requires to perform its intended function.
Electrical circuits of all kinds and sizes, including electronic circuits, require the application of electrical energy for their operation. Batteries of one kind or another have long been used for this purpose. Typically, such a battery provides an output with relatively constant parameters such as, for example, voltage and amperage. Generally, some effort is made to see that the values of the battery output parameters remain substantially constant.
Electrical circuits are typically composed of several different operating components and associated electrical energy conditioning components. These different operating components often have different voltage, amperage and other electrical energy parameter requirements. Many of the components in the circuit are included simply to adjust the various values of the output from the battery to the values that are required by the individual operating components. Much of the energy consumed by the circuit is consumed by the electrical energy conditioning components that tailor the output of the battery to the requirements of the various operating components. Much of the expense and difficulty in the construction of a circuit arises from the need for building in such energy conditioning components that are needed only to tailor the output of the battery to meet the requirements of the individual operating components. The overall size and complexity of a circuit is necessarily adjusted to accommodate the inclusion of these energy conditioning components. The effort to miniaturize circuits is hampered by the need for the inclusion of such energy conditioning components in these miniaturized circuits. If these battery output tailoring components could be eliminated great improvements could be made in circuits of all sizes, purposes, and configurations.
Common failure modes of batteries in general are internal shorting or formation of an open circuit. When battery cells are arranged in a static array, the failure of one cell will generally change the parameters of the electrical energy that can be provided by the array. For example, if one of a set of parallel connected battery cells is removed the amperage of the output drops. If one of a set of series connected battery cells is removed the voltage of the output drops. The failure of a cell through an open circuit may completely disrupt the operation of the battery array (for example, in a series arrangement of cells). The failure of a cell through internal shorting may completely disrupt the operation of the battery array. Each cell that fails or becomes partially compromised changes the parameters further.
The operating components in an electrical circuit are generally designed to operate under substantially constant energy parameters. Thus, when the parameters of the output from the battery array change, because of the loss or malfunction of a cell from the battery array, the circuit either stops operating or performs poorly. Various expedients have been proposed for solving this problem. It has been proposed to lithographically fabricate a battery layer that contains a plurality of individual batteries, and a separate layer that contains a plurality of data processing cells. The two layers are electrically insulated from one another, and each data processing cell is electrically connected to its own battery. See, for example, Norman U.S. Pat. No. 6,154,855.
Norman U.S. Pat. No. 6,154,855 proposes to provide fault tolerance in the array of data processing cells by including redundant data processing cells, automatically eliminating bad processing cells from the circuit, and replacing them with spare cells. There is no indication that any power conditioning components have been eliminated from the circuits in Norman""s data processing cells, or that such elimination would be possible. Norman discloses a data processing system comprising a monolithic redundant network of data processing cells. It is suggested, inter alia, that the monolithic structure could be in the form of a multi-layered thin flexible sheet approximately the size of a credit card. The data processing cells in the network are interchangeable so that duplicate spare cells may be used to provide redundancy. Each cell includes a plurality of components such as, for example, a processor, memory, and input/output means. It is suggested that each cell could also have its own individual battery cell so that there would be full redundancy at the cell level. That is, each data processing cell should have its own individual battery cell in a one-to-one relationship. The battery cells in the expedient proposed by Norman are not fungible as between the data processing cells. This one-to-one relationship would provide a common bus for all of the power consuming components within a data processing cell. It is not likely that all of the components within a cell will operate on the same current and voltage levels. Any adjustment to the power output of the battery cell, which a given component within the data processing cell might require, would have to be provided by power conditioning elements within the circuitry of that data processing cell. It is also suggested by Norman that non-defective neighboring cells in a specific region of the total network might be joined in a power-sharing bus. Whether the proposed connection would be serial or parallel is not clear. Such a common bus with multiple interconnected battery cells would necessarily provide more current or more voltage than a single battery cell could produce, so the power available from a common bus would have different characteristics from that provided from a single battery cell in a single data processing cell. There is no indication as to how power from a common bus could be utilized by individual cells that are designed to run on the output of a single battery cell. Random dynamic connectivity between the individual power consuming components in any given data processing cell, so that each power consuming component has its own individual dynamic fault tolerant power bus is contrary to the teachings of Norman. There is no teaching in Norman that each power consuming component within a data processing cell should have its own individual power bus, and there is no suggestion that there would be any advantage to such an arrangement.
Various expedients had been proposed for providing a dynamic array of battery cells. Harshe U.S. Pat. No. 5,563,002, for example, proposed the use of a programmable battery array with a single output power bus to address the problem of achieving a stable overall voltage or current output despite varying loads and battery charge conditions. Harshe proposes the use of a plurality of discrete cells that are selectively connectable by mechanical switches as the load varies so as to provide a stable output to a single bus. Harshe does not address the problem of dynamically tailoring voltage or current to the individual requirements of each of a plurality of different electrical loads within a single device. Harshe does not suggest that complex electronic devices can be simplified by dynamically interconnecting an array of individual power cells to simultaneously supply different voltages and currents to separate components or modules within a single complex device. Mechanical switches such as those proposed by Harshe are adapted to accommodating high power demand applications on a single bus. Such high power demand applications are, as noted by Harshe, often beyond the capacity of semiconductor switches. Harshe does not suggest that by dynamically forming a plurality of power buses from a single battery array it is possible to reduce the power that each individual bus carries to levels where small, fast, efficient, inexpensive and reliable semiconductor switches can handle the load without recourse to mechanical switches. Mechanical switches do not lend themselves to random dynamic configuration, that is, two individual battery cells can not be selected at random and electrically connected without regard to their physical locations. The geometry of a mechanically switched battery array is confined physically to what is required to accommodate the switches. Harshe does not teach the provision of an individual power bus for each load, which individual bus is formed instantaneously as required from a plurality of power cells that are substantially fungible as between individual power buses. Mechanical switches inherently exhibit relatively slow response times as compared to solid state devices. It is physically impossible to instantaneously reconfigure multiple power busses using mechanical switches. Harshe""s proposed array is not functional as a combined serial-parallel array. If Harshe""s proposed array were to in someway be made functional in a combined serial-parallel configuration, and a cell became defective, there is no disclosed way of bypassing that cell on the serial side.
Fault tolerant distributed battery systems had been proposed previously. See, for example, Hagen et al. U.S. Pat. No. 6,104,967. Hagen et al. is directed to a distributed battery system, and particularly the control system for such a battery system for powering electrical vehicles. The load is typically an electric motor, which is supplied from a common power bus. The objective of Hagen et al. is to supply electrical power of predetermined characteristics on a common bus.
The printing of electrochemical cells on flexible substrates had been previously proposed. See, for example, Shadle et al. U.S. Pat. No. 6,395,043. Bates et al. discloses a high energy density thin film microbattery.
Programmable controllers for controlling the operation of multicell battery power systems had been proposed. See, for example, Stewart U.S. Pat. No. 5,422,558. Stewart discloses a plurality of controlled battery modules on a common power supply bus. See also Gartstein et al. U.S. Pat. No. 6,163,131.
The use of one battery in an array of batteries to charge another battery in the array is purportedly disclosed by Garbon U.S. Pat. No. 5,914,585.
Rouillard et al. U.S. Pat. No. 6,146,778 proposes a number of electrochemical cells selectively interconnected in series or parallel through an integrated interconnect board, and irrespective of cell position. The voltage and current characteristics of the overall assembly of cells are said to be alterable by altering the configuration of the connecting pattern. Rouillard et al. discloses a common bus system.
Conventional semiconductor switch arrays provide as many as several million switches, each having several hundred input/output (I/O) ports, all controlled by a central processor unit (CPU). Switching times can be in the order of nanoseconds. Such conventional semiconductor switch arrays, for example, gate arrays, are programmable and include memory capacity. The ON resistance of the semiconductor switches in such arrays can be in the order of a few milliohms.
Power generating cells of various configurations and types are well known. Electrochemical battery couples such as zinc-manganese dioxide, zinc-silver oxide, lithium-cobalt oxide, nickel-cadmium, nickel-metal hydride, metal-air, and the like, are known. Fuel cell couples, such as hydrogen-oxygen, photovoltaic couples such as P and N doped silicon, nuclear cells (P N or PIN junction with an associated Beta particle emitter such as tritium), and the like are known. Other electrical energy storage devices such as capacitors or inductors (the combination comprises a xe2x80x9ctank circuitxe2x80x9d) are known. Energy transducers that produce electrical current or charge such as, for example, a thermo voltaic cell (for example, bimetallic couple), an inductive element, a capacitive element (for example, a piezoelectric element), thermal, acoustic, vibration, and the like actuated transducers, and radio frequency antenna array to gather radio frequency energy are all known.
Conventional flat, planar or wafer type batteries, a single cell (and its seals) extends across the entire areal projection of the battery. Therefore, when the battery is flexed, the shear forces are additive along the full length of the battery and cell. Consequently, a considerable amount of shear force can be exerted on the cell and its seals. This in turn can cause the cell and battery to short, rupture and leak due to failure of the cell seals, or damage to the battery separator, among other modes of failure.
In a variety of conventional battery driven electrical circuits different voltages and currents are required by the various elements that make up the circuit. Conventional battery systems are normally only capable of supplying nominally one voltage at one maximum current, the variety of voltages and currents that are required by the electrical device is provided by what is referred to as xe2x80x9cpower conditioningxe2x80x9d, or xe2x80x9celectrical energy conditioningxe2x80x9d devices. These devices alter or xe2x80x9cconditionxe2x80x9d the voltage and current (the electrical power) that is generated by the battery. These conditioning devices can be xe2x80x9cpassivexe2x80x9d such as resistors or xe2x80x9cactivexe2x80x9d such as a switching boost converter. The use of these devices is inefficient in that they consume electrical energy to operate, introduce expense (in terms of cost of purchase, as well as cost of handling and placement into the circuit), require increasingly valuable real estate on the circuit board, and increase the probability of overall device failure. It is estimated that in the average consumer battery operated product as much as 60 percent of the component count, and 40 percent of the cost of the electronics is due to the numerous power conditioning devices presently required by such circuitry. If the majority of these power-conditioning devices could be eliminated, then electrical circuitry would be more efficient, less costly, more compact and more reliable.
Many improvements and new developments in electronics could be realized if a battery array that is self healing and dynamically configurable to provide a plurality of instantaneous electrical buses to the individual loads in an electrical circuit could be devised. It would be particularly advantageous if such a battery array could be physically flexible.
A preferred embodiment of the digital battery according to the present invention comprises an array of individual cells, controllably interconnected for instantaneous dynamic configuration into a plurality of power buses having different electrical energy output characteristics, each of which is tailored to supply the energy required at the instant by a particular electrical load within a circuit. Preferably the cells are fungible and randomly available so that at any given instant any given cell can be poweringly associated with a particular electrical load.
A dynamic battery array of the present invention provides increased electrical and physical flexibility, with substantial improvement in battery reliability and efficiency combined with decreased battery and cell production cost. In general, the cost of the product into which the battery array is placed is further reduced in addition to the savings gained from a decrease in battery cost.
A dynamic battery array of the present invention employs low resistance switch arrays for dynamically and instantaneously forming individual power networks or power buses between selected power cells and individual electrical loads in electrical circuits. The low resistance switch arrays (generally less than approximately 0.5, and preferably less than approximately 0.01 ohms of ON resistance per switch) in such dynamic battery arrays are, for example, semiconductor switches, controlled, for example, by a central processor unit (CPU). Preferably several switches are associated with each cell so as to provide the maximum possible electrical flexibility. The operation of the array is preferably programmable. The term xe2x80x9cswitch arrayxe2x80x9d is intended to include the switches, the switch and circuit control elements such as a CPU, memory of all types, thermal and other sensors, associated elements, and the like. The circuits to which such battery arrays are applied are generally complex circuits in which several different loads occur, each of which has a different power requirement. Such battery arrays are also applicable to single load circuits where the power requirements fluctuate or the maintenance of a precise power level is required for the duration of the charge cycle of the battery array. If a considerable excess of cells is provided, individual cells in the array can be swapped in and out to maintain desired power levels during, for example, start-up, or near the end of a charge cycle.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.